Simulator investigation of the effects of l alpha and true speed on longitudinal handling qualities

Abstract

The experimental study conducted was directed toward investigating the effects, on pilot rating and optimum longitudinal control gain, of large variations in the relative amplitude and phase of the basic airplane responses to elevator control and to vertical gusts. The variations in relative amplitude and phase were obtained through changes in true speed and the parameter La = (pSF/2ni)CJr,a. Combinations of V and La were examined for each of three short period poles in a fixed-base simulator. True speed was varied from V = 130 knots to V = 1800 knots and La was varied from La = 0.07 I/sec to 4.01/ sec. The steady state ratio of normal acceleration to angle of attack was found to be of significance both to the flying qualities of an airplane and to the optimum longitudinal control gain. Thus the results of previous investigations of the effect of short period dynamics on longitudinal flying qualities must be qualified since the investigations were conducted at specific values of La and V or nz/a. The longitudinal control gain selected by the pilots was found to be a compromise which weighed the often conflicting requirements for good pitch attitude control, adequate g-limiting protection and satisfactory steady forces in turns. It was demonstrated that the primary factors which determine the normal acceleration response to turbulence are JLa, short period frequency, short period damping ratio, and true speed together with the frequency spectrum characteristics of the turbulence.